There has always been considerable interest in developing methods and apparatus for maximizing the efficiency of energy generating devices. Recently, with the escalating price of fuel, it has become apparent that improvements in efficiency can translate into large cost savings.
Examples of recently developed devices for enhancing the efficiency of energy generating devices can be found in Baudelet De Livois U.S. Pat. No. 3,723,047, issued Mar. 27, 1973; and Shigemura U.S. Pat. No. 4,162,889, issued July 31, 1979. Both of these patents disclose feedback systems for use with furnaces. More particularly, in a prior art feedback system, combustibles in the exhaust line are monitored to determine the efficiency of the engine. If the engine is not burning at maximum efficiency, the air flow to the furnace is adjusted. By adjusting the air flow, efficient burning can be achieved based on a given flow rate of fuel.
Both the above-cited prior art systems are particularly adapted for use with furnace installations where heat is produced to generate steam. Typically, furnace installations are operated at maximum power at all times. Thus, the fuel input rate is held relatively constant, while the air input is adjusted to insure efficient burning. The previously cited patent to Shigemura provides a detailed explanation of the theories of efficient combustion and is incorporated herein by reference.
A furnace installation is typically designed to operate most efficiently at full power. The steam output from the furnace is used to operate various types of machinery. In addition, the steam output can be used to drive turbines for the generation of electricity. In operation, when demand from the machinery drops, the excess steam is simply gated to the turbines to generate electricity. Thus, the system can be operated at full power at all times with no waste of generated steam.
A different situation exists in an installation utilizing an internal combustion engine because there is no easy means for utilizing its excess power capacity. In a typical situation, such as a refinery setting, an internal combustion engine is arranged to power a set of machines which are cycled on and off during the work day. Since the engine is called upon to deliver a wide range of power outputs based on the varying loads, it would be extremely inefficient to run an internal combustion engine at full power during times of reduced load.
Accordingly, in most known internal combustion engine installations, a means is provided for sensing the load on the engine and regulating the fuel flow as a function thereof. This means is generally referred to as a governor and controls the flow of fuel in response to the load on the engine. Unfortunately, the governors found in the prior art consist of relatively crude linkage arrangements which are only capable of making gross adjustments to the flow of fuel.
The inability of the governor to provide accurate adjustments is one factor which, in combination, gives rise to inefficient operation. Another factor contributing to this problem is that the engine must never be supplied with less fuel than is necessary to support the load. More particularly, the engine will tend to stall if supplied with too little fuel, thereby interrupting operations. Accordingly, if the governor were calibrated to closely follow the load, its inherent inaccuracy would frequently result in the stalling of the engine. Thus, in practice, the governor is typically calibrated to deliver slightly more fuel than necessary to prevent stalling. As can be appreciated, the extra fuel supply represents wasted energy.
Another shortcoming associated with the prior art devices relates to the adjustment of the air/fuel ratio. More particularly, in order to obtain maximum performance of an engine, all adjustments, including the air/fuel ratio, are made based on the full load condition. The air/fuel ratio is typically adjusted through a carburetor system wherein fuel flow from the governor is supplied to a carburetor which mixes in air to permit combustion.
In operation, when the governor senses a reduction in the load, it functions to reduce the fuel flow to the carburetor. Since the air/fuel ratio at the carbureator has been adjusted based on maximum fuel flow, the resulting mixture associated with the reduced fuel flow condition will not achieve maximum combustion efficiency.
Accordingly, it would be desirable to provide a method for optimizing the efficiency of an internal combustion engine. Unfortunately, the devices found in the prior art, designed for furnace control, are not suitable for this purpose. More particularly, the prior art devices are designed merely to regulate air flow to a furnace which is being supplied with a relatively constant fuel flow. In contrast, the subject invention is intended to minimize fuel usage in an internal combustion engine subject to varying loads.
Accordingly, it is an object of the subject invention to provide a new and improved apparatus and method for minimizing the fuel usage, in an internal combustion engine system, which is subject to varying load conditions.
It is a further object of the subject invention to provide a new and improved apparatus for minimizing fuel usage in an engine system which includes a governor for adjusting the rate of flow of fuel as a function of load.
It is another object of the subject invention to provide a new and improved apparatus which continuously monitors the combustibles in the exhaust output of an internal combustion engine to premit the fine tuning of the fuel supply for maximizing efficiency.
It is still a further object of the subject invention to provide a new and improved method for continuously monitoring the combustibles in the exhaust output of an internal combustion engine, which functions in combination with a governor to fine tune the fuel supply for maximizing efficiency.
It is still another object of the subject invention to provide an apparatus and method which also improves air quality of the exhaust of an engine and reduces maintenance problems.